Coal treating method and apparatus for coke plants

ABSTRACT

1. IN A METHOD OF OPERATING A COKE PLANT, FEEDING PULVERIZED COAL INTO A COAL DRYER, DIRECTING A HOT DRYING GAS AT A FIRST GIVEN TEMPERATUE UPWARDLY THROUGH THE COAL DRYER AND SUSPENDING THE PULVERIZED COAL IN THE UPWARDLY FLOWING DRYING GAS TO FORM A FLUIDIZED BED, CIRCULATING A DRYING FLUID THROUGH COAL BY CONTACT WITH THE COILS, HEATING THE DRYING THE COAL BY CONTACT WITH THE COIL, HEATING THE DRYING FLUID CIRCULATED THROUGH THE COILS AT LEAST INDIRECTLY WITH HEAT EXTRACTED FROM HOT COKE SHORTLY AFTER THE COKE IS DISCHARGED FROM A COKE OVEN, TRANSPORTING DRY COAL AT A SECOND GIVEN TEMPERATURE FROM THE COAL DRYER INTO A HEATER, EXPOSING THE DRY COAL IN THE HEATER TO A HEATING GAS AT A TEMPERATURE SUBSTANTIALLY HIGHER THAT SAID FIRST AND SECOND GIVEN TEMPERATURES AFTER PRELIMINARILY HEATING THE LATTER GAS WITH HEAT EXTRACTED FROM THE HOT COKE, AND   DELIVERING THE DRY, HEATED COAL TO A COKE OVEN SO THAT THE COAL IS RECEIVED AT THE OVEN IN A DRY, PREHEATED CONDITION.

O 1974 R. KEMMETMUELLER 3,843,458 COAL TREATING METHOD AND APPARATUS FORCOKE PLANTS 3 Sheets-Sheet 1 Filed April 13, 1973 com. TREATING METHODAND APPARATUS FOR com: PLANTS Filed April 13, 1973 Oct. 22, 1974. R.KEMMETMUELLER 5 Sheets-Sheet 2 COAL TREATING METHOD AND APPARATUS FORCOKE PLANTS Filed April 15; 1973 Oct. 22, 1974 R. KEMMETMUELLER 3Sheets-Sheet 3 'III United States Patent O 3,843,458 COAL TREATINGMETHOD AND APPARATUS FOR COKE PLANTS Roland Kemrnetmueller, Pittsburgh,Pa., assignor to American Waagner-Biro Company, Inc., Pittsburgh, Pa.

Continuation-impart of application Ser. No. 224,154, Feb. 7, 1972, nowPatent No. 3,728,230. This application Apr. 13, 1973, Ser. No. 350,961

Int. Cl. Cb 39/02 US. Cl. 20139 Claims ABSTRACT OF THE DISCLOSURE A coaltreating method and apparatus for coke plants, according to which coalis delivered to coke ovens in a dry, preheated condition. Pulverizedcoal is fed to a coal dryer in which the coal is suspended in afluidized bed of heated gaseous material while in the coal dryer thecoal is free to move into contact with coils through which a dryingfiuid is circulated. A dry-quenching gas is circulated through a body ofhot coke shortly after pushing of the latter from a coke oven, so thatthe dry-quenching gas extracts heat from the hot coke, and it is thisheat which is used to heat the drying fluid. From the coal dryer, thecoal in a fully dry condition is delivered to a heater which alsoreceives its heat from the heat energy extracted from the body of hotcoke by the dry-quenching gas, and in this heater the temperature of thedry coal is raised, so that coal in a dry heated condition issues fromthe heater. From the latter the coal is transported to the coke ovens sothat in this way the coke ovens are charged with dry, preheated coal,with the energy which is used for this purpose being taken from the hotcoke which is discharged from the coke ovens.

CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of copending application Ser. No. 224,154, filedFeb. 7, 1972 and entitled Coke Plant and Method for Operating Same.

BACKGROUND OF THE INVENTION The present invention relates to cokeplants.

In particular, the present invention relates to the treatment of coalwhich is to be converted into coke in the coke plant.

As is well known, the treatment of the coal in preparation forconverting the latter into coke is an extremely important phase of theoperation of a coke plant. The output of any given coke plant will ofcourse be determined by the operating cycles at the coke batteries. Theshorter the time required for converting the coal into coke at the cokeovens, the greater the output. Moreover, it is known that a higherquality coke can be achieved from coal which is in a given conditionprior to distillation in the coke ovens.

A further factor which is of great importance is the necessity ofreducing pollution of the surrounding atmosv phere to the greatestpossible extent. One of the greatest sources of pollution at the presenttime in the operation of coke plants is the result of the handling ofthe coke as it is discharged from the coke ovens and the handling of thecoal during transportation and treatment thereof in reparation forcharging the coke ovens.

While it is possible to improve the above factors, at the present timethe available expedients for this purpose involve considerable costs sothat if steps are taken to reduce pollution and to treat the coal so asto achieve coke of superior quality with a high output, the result is anundesirably high operating cost.

Patented Oct. 22, 1974 It is accordingly a primary object of the presentinvention to provide a method and apparatus which will avoid the abovedrawbacks.

Eln particular, it is an object of the present invention to provide amethod and apparatus which make it possible to achieve coke of highquality at relatively low cost.

Also it is an object of the present invention to provide a method andapparatus capable of achieving a high output of coke, also at relativelylow cost.

Furthermore, it is an object of the present invention to provide amethod and apparatus which will protect the atmosphere against pollutionwithout involving any extremely high cost.

In particular, it is an object of the present invention to takeadvantage of energy which is present in the form of heat in coke whichis discharged from the coke ovens, and making use of this energy for thepurpose of achieving the above objects at a relatively low cost.

According to the present invention pulverized coal is fed to a coaldryer in which the pulverized coal is suspended in an upwardly directedhot drying gas so as to form a fluidized bed. A drying fluid iscirculated through coils in the fluidized bed in order to further drythe coal by contact with these coils. The drying fluid which iscirculated through the coils is heated at least indirectly with heatwhich is extracted from hot coke shortly after the latter is dischargedfrom a coke oven. The dry coal is transported from the coal dryer to aheater where the dry coal is exposed to a heating gas which has beenpreliminarily heated with heat from the hot coke, so that in this way adry, preheated coal is achieved to be delivered in this dry, preheatedcondition to the coke battery.

The coke plant of the invention includes a coal-drying means for dryingpulverized coal. A heating means communicates with the coal-drying meansfor receiving the dry coal therefrom and for heating the dry coal. Abunker is provided to receive hot coke from a coke oven. A heattransfermeans communicates with this bunker, with the coal-drying means, andwith the heating means for extracting heat from the coke in the bunkerand for delivering the extracted heat in part to the coal dryingmeansand in part to the heating means for drying the coal at least in partwith heat extracted from the hot coke in the bunker and for heating thecoal at the heating means with heat extracted from the coke in thebunker. A transporting means communicates with the heating means totransport the coal in hot, dry condition from the heating means to acoke battery, so that the coal is received at the coke battery in dry,preheated condition.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a schematic illustration of one possible method and apparatusaccording to the present invention;

FIG. 2 is a schematic illustration of a variation of the method andapparatus illustrated in FIG. 1; and

FIG. 3 is a schematic illustration of a third embodiment of a method andapparatus according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there isschematically illusstrated therein, at the upper right part of FIG. 1, abunker 10 which receives in a known way hot coke immediately subsequentto pushing of the coke from a coke oven. The hot coke in the bunker 10is cooled therein prior to being discharged in a known way by way of thevalves 12 and 14 so that the relatively cool coke will be received on aconveyer means 16 to be conveyed to suitable bins where the coke ismaintained in readiness to be used for such purposes as blast furnaceoperations, for example.

The hot coke which is received in the bunker contains a tremendousamount of energy. In many conven tional coke plants this energy iswasted, particularly in the case where the coke is cooled bywet-quenching procedures. Thus, it is known to cool the hot cokeimmediately subsequent to discharge thereof from a coke oven with liquidwhich creates great clouds of steam, creating undesirable pollution ofthe surrounding atmosphere and wasting the energy which is contained inthe heat of the hot coke.

Therefore, dry-quenching of the hot coke is far more preferable, and inthe method and apparatus shown in FIG. 1 dry-quenching is provided witha dry-quenching gas. The dry-quenching gas, which may if desired be asuitable inert gas, is directed along a closed circuit indicated by thedot-dash line in FIG. 1, as explained by the code at the lower rightportion of FIG. 1. The dryquenching gas is circulated through the closedpath by a suitable blower 18 or the like. This lower 18 delivers thedry-quenching gas through a conduit 20 to a cyclone 22 in which anyparticles of coke entrained in the gas are separated, these particles ofcoke being delivered to a collecting bin 24 from which they aretransported by a suitable screw conveyer 26 or the like to any desiredlocation where the fine particles of coke will be used.

From the cyclone 22 the dry-quenching gas continues to travel through apipe 28 to a supply header 30 in the form of a ring having suitablevalves and communicating through pipes 32 with an inlet 34 in theinterior of the bunker 10. The inlet 34 in a known way has the baflles36 between which the dry-quenching gas escapes with these bafflespreventing the travel of the dry-quenching gas into the body of cokefrom being obstructed.

The dry-quenching gas enters the bunker 10 at a temperature ofapproximately 150 C, as indicated in FIG. 1, and after travellingupwardly through the hot coke, the dry-quenching gas discharges from thebunker 10 into the discharge pipe 38 at a temperature of approximately800 C., for example. At this latter temperature the dryquenching gaswill reach the top of an elongated vertical housing 40 down which thedry-quenching gas flows to discharge out of the housing 40 into an inletpipe 42 which returns the dry-quenching gas to the blower 18. Thus, thedry-quenching gas has been cooled from 800 C. to a temperature of 150 C.in the illustrated example before being returned to the bunker 10. Asthe dryquenching gas travels down the housing 40, it gives up its heatto various heat exchangers, economizers, and the like, which aredistributed along the interior of the housing 40 in a manner describedin greater detail below.

As the hot dry-quenching gas flows downwardly along the interior of thetubular housing 40, it first flows across a heat exchanger 44, thenacross additional heat exchangers or economizers 46 and 48, and so onacross additional heat exchangers or economizers 50, 52, and 54. Beforedischarging out of the housing 40 into the pipe 42 in order to bereturned back to the blower 18, the dry-quenching gas flows also acrossan additional heat exchanger 56. All of the above heat-exchanger unitsin the housing 40 successively cool the dry-quenching gas so that it isreturned to the bunker 10 at a temperature of approximately 150 C. whileissuing from the bunker 10 at a temperature of approximately 800 C., inthe illustrated example, as pointed out above. Through this series ofheat exchangers energy is extracted from thp dry-quenching gas, and thusthrough the latter from the hot coke in the bunker 10, so that furtheruse may be made of this energy.

After flowing downwardly past the first heat exchanger 44, thetemperature of the dry-quenching gas is reduced in the above example toapproximately 250. The heat ex changer 46 forms part of a closed pathfor a drying fluid which in the illustrated example is steam, thisdrying fluid flowing through coils 58 situated in a coal dryer 60. Thecoal dryer 60 is in the form of a suitable container to which pulverizedcoal is fed by way of a feeding means 62 part of which is illustratedschematically in FIG. 1. Thus, coal in pulverized condition is conveyedin any suitable way to the inlet 62 from which the pulverized coal dropsdown into the interior of the closed vessel 60. The coils 58 aredistributed through the container 60 so that the particles of pulverizedcoal will engage the coils 58. The bottom of the container 60communicates with a pipe 62 by which a hot drying gas is directedupwardly through the interior of the container 60. This hot drying gasis taken from any suitable source such as a source of waste gas, thisgas arriving at a temperature of approximately 150 C., for example, to ablower 64 which delivers the drying gas to the heat exchanger 50 so thatin the latter the temperature of the gas will be elevated to a range of250450 C., in the illustrated example, before reaching the container 60.The blower 64 assures that the gas has a suflicient pressure to be ableto suspend the pulverized coal particles to form a fluidized bedtherefrom. As is well known the gas may be delivered to a lower plenumdefined at its upper end by a perforated plate through which streams ofdrying gas issue upwardly to form the fluidized bed in a well knownmanner. The particles of coal move about in the fluidized bed so as tocontact the coils 58 a number of times, and in this way the coal isdried not only by the drying gas which forms the fluidized bed but alsoby contact with the coils 58.

The fluid in the coils 58 also flows in accordance with the inventionalong a closed path, this path being desig nated by the dash-dot-dotline, as is apparent from the code at the lower right of FIG. 1. Thusupon discharging from the coal dryer 60 the drying fluid will flow alonga pipe 68 to a condensate tank 70 from where the condensed liquid flowsto a pump 72 in order to be pumped thereby along the pipe 7 4 into theheat exchanger 54 from which the pumped fluid flows to a second heatexchanger 52 and then along a pipe 74 to the steam drum 76. From thesteam drum 76, from which steam may be taken for other purposes also,the fluid circulates through the heat exchanger 48 by way of a pair ofpipes 78 and 80. A branch from the pipe 78 directs some of this fluidthrough the heat exchanger 46 from which the heated fluid at atemperature of 250, for example, flows along the pipe 82 to the coils S8to progress along these coils to the pipe 68, in this way completing theclosed path for the drying fluid.

The drying gas from the fluidized bed flows out through an outlet 84 atapproximately a temperature of 100 C. This gas then flows through aVenturi scrubber 86 from which moisture with particles of coal isdischarged by a pipe 88, and a desmister 90 condenses further liquid outof the discharging gas to flow also along the pipe 88 to any suitablereceptacle. A heater 92 is provided to raise the temperature of the gasbefore it is vented at 94 to the outer atmosphere. In this way this gashas been cleaned before being released to the outer atmosphere.

From the coal-dryer 60, the pulverized coal in dry condition flowsthrough a supply conduit 96 at a temperature of approximately 100 C. tothe inlet of an elongated heating means 98 which may be a flash heater,for example. The pipe 96 is in the form of a pneumatic conveyor for thepulverized dry coal particles. Thus, the coal is completely dry by thetime it reaches the heating means 98. This heating means 98 is in theform of an elongated hollow container having the inlet end to which thedry coal is delivered by the conveyer 96.

The heating gas which flows along the interior of the heating means 98is preferably an inert gas such as nitrogen or a mixture of nitrogen andcarbon dioxide. This heating gas reaches the inlet of the heating means98 at a temperature of approximately 650 C., in the illustrated example.The heating gas is heated by the first heat exchanger 44 to an extremelyhigh temperature on the order of 650 in the illustrated example. Thus,from the heat exchanger 44 the heating gas flows through the pipe 100 tothe inlet of the heating means 98. This gas flows through the heatingmeans 98 at a speed of approximately 60 meters per second, so that thepulverized coal is conveyed along the interior of the heating means 98to issue at the outlet thereof into a cyclone 102. The pipe 104 connectsthe discharge end of the heating means 98 with the cyclone 102, and atthis pipe 104, which may be provided with a suitable valve 106, the coalhas a temperature of approximately 250 C.

The heating gas is also directed along a completely closed pathdesignated by the dash-dot-dot-dot line, as shown by the code at thelower right of FIG. 1. From the cyclone 102 the heating gas flows withany additional smaller coal particles to an additional cyclone assembly108, and from the latter the heating gas flows into the lower end of abag filter assembly 110 or the like where cleaning of the gas takesplace. A part of the gas may be vented to the atmosphere through a vent112. However, the greatest part of the gas flows from the filter 110along a pipe 114 back to a blower 116 from which the gas is delivered tothe heat exchanger 44 in order to again be raised to the elevatedtemperature on the order of 650 C. in the illustrated example beforeagain reaching the heating means 98. In this way the heating gas is alsodirected along a closed path.

The above method and apparatus of the invention are completed by anumber of added features. Thus, make-up water is added to the pump 73through an inlet 118.

Also, part of the inert gas with fine coal dust suspended therein isdelivered by a pipe 120 from the filter 110 to an auxiliary burner 122which may be operated to regulate the temperature of the dry-quenchinggas before it reaches the heat exchanger 40. For example, toward the endof a cooling cycle it may happen that the temperature of thedry-quenching gas falls below a desired value. At this time theauxiliary burner 122 may be used to increase the temperature of the gasso that the heat exchanger 44 will receive a sufiicient amount of heatto provide the desired temperature in the heating gas.

Of course, the coal dust is suspended in the pipe 120 in an inertatmosphere. Combustion air for the burner 122 is derived by way of ablower 124 which conveys air from an inlet 126 through a pipe 128 intothe heat exchanger 56 in which the air is preheated before flowing alonga pipe 130 to the burner 122 in order to provide at the burner 122combustion air to regulate the temperature of the dryquenching gas.

Also, part of this preheated combustion air may be branched through apipe 132 to an additional burner 134 which also receives coal dustsuspended in the inert gas by way of a conduit 136, and thus by way ofthe auxiliary burner 134 it is also possible to regulate the temperatureof the heating gas before it reaches the heating means 98.

In addition, those fairly large coal particles which are too heavy to becarried along with the heating gas flow automatically to a crusher 138which further pulverizes these particles and directs them back through arecirculating pipe 140 to the inlet of the heating means 98.

The dry, preheated coal is delivered from the cyclones 102, 108 to aconveyer 142, such as a suitable screw conveyer, which delivers the coalto a bin 144 in which the coal is temporarily stored for a relativelyshort time before being delivered by the larry car units 146 to an ovenof the coke battery 148.

According to a further feature of the invention part of the inert gasdischarging from the heating means 98 is diverted by a branch pipe 150to the bin 144 so that this inert gas which is at a temperatureapproximately 250 C. in the illustrated example serves on the one handto contribute toward maintaining the coal at its eleveated temperatureand on the other hand to prevention of any explosions. For the purposeof maintaining the coal at the bin 144 at the desired temperature, thebin 144 may be surrounded by a jacket 152 to which steam is suppliedthrough an inlet 154, from any suitable source, this steam dischargingthrough the outlet 156 and being again heated in any way beforereturning to the inlet 154. Thus maintenance of the dry coal at theelevated temperature is assured with the method and apparatus of theinvention so that perfectly dry pulverized coal at an elevatedtemperature on the order of 250 C. reaches each coke oven of the cokebattery.

It has been found from experience that with the above method andapparatus of the invention fully 50% of the heat energy available in thehot coke in the bunker 10 is utilized for the various drying and heatingoperations referred to above. Furthermore, it has been found that theoperating time required at each of the coke ovens can be reduced by 40%because of the treatment of the coal according to the method andapparatus of the present invention, so that in this way the output of agiven coke battery will be greatly increased with the present invention.Furthermore it will be noted that no Where is there any escape ofpollutants to the outer atmosphere, so that the method and apparatus ofthe invention have the additional advantage of enhancing the quality ofthe atmosphere.

Of course, it is possible to achieve still additional use from theavailable energy as by utilizing steam issuing fgom the steam drum 76for other purposes, as pointed out a ove.

The embodiment of the method and apparatus which is illustrated in FIG.2 of the drawings is identical with that of FIG. 1 except for the dryingfluid which is circulated through the coils 58 in the coal dryer 60 andthe manner in which this drying fluid is heated. In the embodiment ofFIG. 2, the drying fluid is in the form of a suitable liquid such as oilor glycerine. The coils 58 communicate with a pa1r of pipes 160 and 162which in turn communicate with a suitable heat exchanging coil 164. Apump 166 is connected for example to the pipe 162 for continuouslycirculating the drying liquid through the coils 58 and through the heatexchanging coil 164 which is schematically represented in FIG. 2. Theheat exchanging coil 164 is in heat exchanging relationship with avessel 168 in which circulates another heat-exchanging fluid such as asuitable liq- 111d, steam, or the like, this latter fluid being heatedby way of a heat exchanger 170 in the housing 40. Thus, this heatexchanger 170 may be in the form of a simple set of coils across whichthe dry-quenching gas flows to heat the fluid in these coils, this fluidbeing, for example, water which is converted into steam and thencondenses before flowing back to the lower end of the coils 170, so thatin this way there rs a natural circulation of the heating fluid invessel 168 which transfers its heat to the liquid in the coil 164 WhlCh1S continuously pumped through the coils 58. Of course, with theembodiment of FIG. 2 the drying fluid circuit does not require theseries of economizers or heat exchangers 46, 48, 52, 54, or thecondensate tank 70 and the pump 72. Thus, a simpler arrangement isprovided for heating a drying liquid which continuously circulatesthrough the coils 58, but in this case also it is to be noted that theheat is derived, although indirectly, from the dryquenching gas whichextracts the heat from the hot coke 1n the bunker 10.

Except for these differences the embodiment of FIG 2 15 the same as thatof FIG. 1.

As Was indicated above in connection with FIG. 1, the dry-quenching gasis preferably an inert gas, such as car bon dioxide or a mixture of thelatter with nitrogenTand according to the embodiment of FIG. 3 thedry-quenching gas tself serves as the heating gas for heating thepulverized dry coal in the heating means 98. Thus, referring to FIG. 3it will be seen that the housing 40 is replaced by an upper housingsection 172 communicating with a lower housing section 174 by way of aconnecting pipe 176 through which the dry-quenching gas flows downwardlyafter giving up some heat to a heat exchanger 178 which may be used as asource of steam for any desired purpose with this embodiment. From thepipe 176 some of the dry-quenching gas is branched along a pipe 180 toflow therethrough into the heating means 98 where the gas also enters ata temperature of approximately 650 C. in the illustrated example, andfrom the heating means 98 the heating gas in this embodiment alsoconveys the heated dry coal to the cyclones 102 and 108 from which thecoal is delivered to the bin 144 in the same way as described above.Part of the heating gas is also diverted to the bin 144 for the purposesreferred to above, and of course the bin 144 may also be further heatedby way of a steam jacket 152 as described above. While part of the gasmay be cleaned at the filter 110 and vented to the outer atmosphere,most of the heating gas flows from the filter 110 through the pipe 182back to the blower 18 with this part of the dry-quenching gas alsoreaching the blower 18 at a temperature of approximately 150 C. as isthe case with the dry-quenching gas returned through the pipe 42 in themanner described above. Thus the heating gas is recircullated togetherwith the remainder of the dry-quenching gas through the bunker in theembodiment of FIG. 3. In this way it becomes unnecessary to provide anadditional heating gas which is separate from the dry-quench mg gas.

Also, with the embodiment of FIG. 3, the drying fluid which circulatesthrough the coils 58 in the dryer 60 is delivered to the coils 58through a supply conduit 184 while flowing out of the coils 58 through adischarge conduit 186 which delivers the drying fluid to a circulatingpump 188. Through this circulating pump the drying fluid is circulatedthrough a heat exchanger 190 to return in heated condition to the supplypipe 184. In this case the drying fluid may also be steam which isheated at the heat exchanger 190 with heat taken from the dry-quenchingfluid which flows through the lower housing portion 174 in the exampleof FIG. 3. In this case also the steam which flows through the coils 58can be delivered to the latter at a temperature on the order of 250 C.

With the embodiments of FIGS. 2 and 3 it is also possible to achieve theadvantages set forth above in connection with FIG. 1, with respect tothe economy of the operation, utilizing approximately 50% of theavailable heat in the hot coke and reducing the operating time at thecoke ovens by approximately Also with the embodiments of FIGS. 2 and 3there is no discharge of pol lutants to the outer atmosphere.

Thus, with all of the embodiments of the invention the heat energyavailable from the hot coke is used to a very large degree, so thatwaste of this valuable source of energy is reduced to a great extent. Inaddition, experience has shown that perfectly dry pulverized coal at theabove temperature on the order of 250 C. is capable of producing thehighest quality coke, enhancing operations such as those which areencountered in a blast furnace, so that a very superior quality of cokeis achieved with the method and apparatus of the invention.

What is claimed is:

1. In a method of operating a coke plant, feeding pulverized coal into acoal dryer, directing a hot drying gas :at a first given temperatureupwardly through the coal dryer and suspending the pulverized coal inthe upwardly flowing drying gas to form a fluidized bed, circulating adrying fluid through coils in the fluidized bed for further drying thecoal by contact with the coils, heating the drying fluid circulatedthrough the coils at least indirectly with heat extracted from hot cokeshortly after the coke is discharged from a coke oven, transporting drycoal at a second given temperature from the coal dryer into a heater,exposing the dry coal in the heater to a heating gas at a temperaturesubstantially higher than said first and second given temperatures afterpreliminarily heating the latter gas with heat extracted from the hotcoke, and

delivering the dry, heated coal to a coke oven so that the coal isreceived at the oven in a dry, preheated condition.

2. In a method as recited in claim 1, circulating a dryquenching gasalong a closed path through the hot coke, and utilizing heat in thedry-quenching gas as a source of heat for the drying fluid which iscirculated through the coils in the coal dryer and for the heating gasto which the dry coal is exposed in the heater.

3. In a method as recited in claim 2, circulating the heating gas alonga closed path which intersects the closed path along which thedry-quenching gas is circulated while placing the gases inheat-exchanging relation at the place where said paths intersect.

4. In a method as recited in claim 3 and wherein the heating gas is aninert gas.

5. In a method as recited in claim 4 and wherein the heating gas isselected from the group consisting of nitrogen and mixtures of nitrogenand carbon dioxide.

6. In a method as recited in claim 2, branching part of thedry-quenching gas from said closed path and utilizing the brancheddry-quenching gas as the heating gas.

7. In a method as recited in claim 6, returning the brancheddry-quenching gas after exposing the dry coal thereto at the heater backto the closed path for recirculation with the remainder of thedry-quenching gas through the hot coke.

8. In a method as recited in claim 2, circulating the drying fluid alonga closed path and heating the drying fluid at the latter closed pathwith heat extracted from the dry-quenching gas.

9. In a method as recited in claim 8, wherein the drying fluid is steamand is circulated along a closed path which intersects the closed pathalong which the dry-quenching gas is circulated and which is inheat-exchanging relation with the dry-quenching gas at the locationwhere said paths intersect.

10. In a method as recited in claim 8 and wherein the drying fluid is aliquid.

11. In a method as recited in claim 10 and wherein said liquid is placedin heat-exchanging relation with a further fluid which is heateddirectly by the dry-quenching gas.

12. In a coke plant, coal-drying means for drying pulverized coal Whileraising the temperature thereof to a given value, heating meanscommunicating with said coaldrying means for receiving dry coaltherefrom and for heating the dry coal to a temperature substantiallyhigher than said given value, a bunker for receiving hot coke from acoke oven, heat-transfer means communicating with said bunker, with saidcoal-drying means, and with said heating means for extracting heat fromcoke in the bunker and for delivering the extracted heat in part to saidcoal-drying means and in part to said heating means for drying the coalat least in part with heat extracted from the hot coke in the bunker andfor heating the coal at said heating means with heat extracted from thecoke in the bunker, and transporting means communicating with saidheating means for transporting coal in hot, dry condition from saidheating means to a coke oven battery, so that the coal is received atthe coke oven battery in dry, preheated condition.

13. The combination of claim 12 and wherein said heat-transfer meansincludes a quenching gas circulating means for circulating adry-quenching gas along a closed path through said bunker to extractheat from hot coke therein, a drying fluid circulating means includingcoils situated in said coal-drying means for at least partly drying coalby contact between the latter and said coils, said drying fluidcirculating means providing a closed path for a coal-drying fluid, andheating-gas circulating means for circulating a heating gas through saidheating means to heat coal therein, said heat-transfer means furtherincluding a pair of heat exchanger means one of which provides transferof heat from said quenching gas circulating means to said drying fluidcirculating means and the other of which provides transfer of heat fromsaid quenching gas circulating means to said heating gas circulatingmeans.

14. The combination of claim 13 and wherein said one heat exchangermeans is situated subsequent to said other heat exchanger means in thepath of fiow of the dryquenching gas from said bunker out of the latterand back to said bunker so that said other heat exchanging means coolsthe dry-quenching gas before said one-heat exchanging means extractsheat therefrom.

15. The combination of claim 14 and wherein said coaldrying meansincludes a container and means for directing upwardly through the lattera hot gas which will maintain pulverized coal suspended therein to forma fluidized bed in which the coal particles will be dried not only bythe fluidizing gas but also by contact with said coils.

16. The combination of claim 15 and wherein said means for directing thehot fiuidizing gas upwardly into said coal-drying means includes anadditional heat exchanger situated along the closed path of thedry-quenching gas for extracting further heat from the latter to be usedto achieve drying from the fluidizing gas.

17. The combination of claim 16 and wherein said additional heatexchanger is situated in the path of flow of the quenching gas out ofthe bunker and back to the latter subsequent to the other heatexchangers for extracting heat from the quenching gas only after heathas been extracted therefrom for the heating gas and drying fluid.

18. The combination of claim 13 and wherein said transporting meansincludes a bin in which the dry, preheated coke is temporarily storedfor a relatively short time just prior to being charged into the cokeovens of a coke battery, and a branch conduit communicating with saidbin and said heating-gas circulating means for directing a part of thelatter gas to said bin.

19. The combination of claim 18 and wherein the heating gas is an inertgas such as nitrogen, to prevent explosions at said bin and to reducethe rate of cooling of coal in said bin.

20. In a method as recited in claim 4 and wherein just prior to deliveryof the dry, heated coal to a coke oven, the latter coal is temporarilystored for a short time in a bin, and delivering part of the inertheating gas to the latter bin for preventing explosions at the bin andfor maintaining the coal at the bin at an elevated temperature.

References Cited UNITED STATES PATENTS 2,658,862 11/1953 Horner 202 X1,854,407 4/1932 Janeway 202150 FOREIGN PATENTS 1,086,670 8/1960 Germany202-228 NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant ExaminerUS. Cl. X.R.

1. IN A METHOD OF OPERATING A COKE PLANT, FEEDING PULVERIZED COAL INTO ACOAL DRYER, DIRECTING A HOT DRYING GAS AT A FIRST GIVEN TEMPERATUEUPWARDLY THROUGH THE COAL DRYER AND SUSPENDING THE PULVERIZED COAL INTHE UPWARDLY FLOWING DRYING GAS TO FORM A FLUIDIZED BED, CIRCULATING ADRYING FLUID THROUGH COAL BY CONTACT WITH THE COILS, HEATING THE DRYINGTHE COAL BY CONTACT WITH THE COIL, HEATING THE DRYING FLUID CIRCULATEDTHROUGH THE COILS AT LEAST INDIRECTLY WITH HEAT EXTRACTED FROM HOT COKESHORTLY AFTER THE COKE IS DISCHARGED FROM A COKE OVEN, TRANSPORTING DRYCOAL AT A SECOND GIVEN TEMPERATURE FROM THE COAL DRYER INTO A HEATER,EXPOSING THE DRY COAL IN THE HEATER TO A HEATING GAS AT A TEMPERATURESUBSTANTIALLY HIGHER THAT SAID FIRST AND SECOND GIVEN TEMPERATURES AFTERPRELIMINARILY HEATING THE LATTER GAS WITH HEAT EXTRACTED FROM THE HOTCOKE, AND